After running the length of New Zealand last year as a fundraiser for the Stroke Foundation, Mr Brown (39) began his Japanese jog in the southern-most part of the country on April 1.
He ran up to the tsunami-affected Miyagi prefecture, before driving to the north and running back down to Miyagi, to finish in Kesennuma last Friday.
He completed the 4259km distance over 97 days - with just 14 days off along the way, covering an average daily distance of 51.3km and raising about $25,000 for Japan's disaster-hit areas.
Mr Brown, a plumber, translator and ski/snowboard course builder based mainly in Japan and Australia, said it was an "amazing" feeling to cross the finish line.
"I came into the biggest surprise of a finish ever . . . around 50 or 60 people were there, banners and New Zealand flags were up and lots of smiles to welcome us in," he said.
"Just like the New Zealand run, I was crying a bit inside, just to have made it again and have no real problems, no hiccups or stops that changed the plan. It went perfect."
The only real low point for Mr Brown was getting a compression fracture in his spine from pushing his gear buggy, but after two gruelling weeks spent walking for up to 11 hours a day to keep to schedule, the running resumed.
The people he met along the way, particularly those affected by the 2011 tsunami, provided the most special moments.
"They are so positive and happy even though they have lost everything and some family members.
"I got so much power from them and I really think that the world could learn from them and this disaster."
Next stop for Mr Brown is India for next month's "La Ultra - The High" race, the highest altitude ultra-marathon in the world, which only a handful of people qualify for.
The event is 222km long and has to be completed within 60 hours.
"I will give it a shot, for sure. I've just done some great training for it running Japan, so hopefully that will help."
After India, Mr Brown plans to visit friends and family in Wanaka before getting back to work and contemplating his next adventure.
"I'm always thinking of what to do or where to go next, so any ideas, let me know."
